Table 1

Odds ratios for childhood leukaemias and lymphomas (conditional logistic regression)

Variable
Categories
Cases,Controls*
Unadjusted OR (95% CI)
Adjusted OR (95% CI)
Cases, Controls*
Unadjusted OR (95% CI)
Adjusted OR (95% CI)

Leukaemias
Acute lymphoblastic leukaemia (ALL)
Acute non-lymphoblastic leukaemia (ANLL)
Parity
0
71,82
1.0
1.0
15,17
1.0
1.0

1
74,61
1.4 (0.9–2.2)
1.4 (0.9–2.3)
11,16
0.7 (0.2–2.0)
0.8 (0.2–2.6)

2
48,49
1.1 (0.7–1.9)
1.2 (0.7–2.0)
6,5
1.6 (0.4–6.2)
1.7 (0.4–7.8)

≥ 3
22,23
1.1 (0.5–2.1)
1.1 (0.6–2.2)
14,8
2.7 (0.7–9.7)
2.1 (0.5–8.0)

Continuous analysis§ 1.00 (0.85–1.16), p = 0.96
Continuous analysis§ 1.21 (0.93–1.58), p = 0.16
Social class||
I or II
45,44
1.0 (0.6–1.7)
-
6,12
0.5 (0.1–1.7)
-

III
79,66
1.2 (0.8–1.9)
-
16,19
0.6 (0.2–1.9)
-

IV
58,71
0.8 (0.5–1.3)
-
22,13
1.7 (0.6–4.7)
-

V or VI
74,75
1.0
-
19,19
1.0
-

Continuous analysis§ 0.97 (0.86–1.09), p = 0.60
Continuous analysis§ 1.23 (0.92–1.64), p = 0.17
Marital status
Married
250,241
1.3 (0.8–2.2)
1.5 (0.9–2.6)
55,59
0.7 (0.3–1.6)
0.8 (0.3–1.9)

Unmarried
28,37
1.0
1.0
16,12
1.0
1.0
Father's age (years)
<25
58,51
1.1 (0.7–1.8)
1.2 (0.8–1.9)
18,14
1.4 (0.5–4.1)
1.5 (0.5–5.0)

25–29
106,108
1.0
1.0
17,18
1.0
1.0

30–34
59,50
1.2 (0.8–1.9)
1.2 (0.8–1.9)
14,21
0.7 (0.2–2.1)
0.8 (0.2–2.9)

35–39
28,31
0.9 (0.5–1.7)
1.0 (0.6–1.9)
6,9
0.7 (0.2–2.9)
0.9 (0.2–4.5)

40+
6,17
0.4 (0.1–1.0)
0.4 (0.1–0.9)
9,2
4.5 (0.8–25.0)
4.7 (0.8–29.0)

Continuous analysis§ 0.97 (0.94–1.00), p = 0.10
Continuous analysis§ 1.03 (0.98–1.09), p = 0.23
Mother's age (years)
<20
29,23
1.2 (0.7–2.2)
1.4 (0.7–2.8)
7,11
0.6 (0.2–2.2)
0.5 (0.1–2.0)

20–24
91,107
0.8 (0.5–1.2)
0.8 (0.5–1.2)
24,17
2.4 (0.9–6.4)
3.7 (1.2–11.7)

25–29
104,97
1.0
1.0
17,24
1.0
1.0

30–34
41,34
1.2 (0.7–2.0)
1.1 (0.6–1.9)
14,14
1.5 (0.6–4.0)
1.8 (0.6–5.4)

35+
13,17
0.7 (0.3–1.5)
0.6 (0.2–1.3)
9,5
3.3 (0.7–14.3)
2.6 (0.5–13.3)

Continuous analysis§ 0.99 (0.96–1.03), p = 0.78
Continuous analysis§ 1.01 (0.95–1.08), p = 0.64
Urban status
Urban
175,185
0.9 (0.6–1.2)
0.9 (0.7–1.3)
51,50
1.1 (0.5–2.1)
1.2 (0.6–2.7)

Non-urban
101,91
1.0
1.0
20,21
1.0
1.0

Lymphomas
Non-Hodgkin's lymphomas
Hodgkin's disease**
Parity
0
27,23
1.0
1.0
47,38
1.0
-

1
8,14
0.4 (0.1–1.3)
0.3 (0.1–1.2)
43,46
0.8 (0.4–1.4)
-

2
15,11
1.0 (0.4–2.9)
1.2 (0.4–3.6)
29,34
0.7 (0.3–1.3)
-

≥ 3
12,14
0.6 (0.2–1.9)
0.6 (0.2–1.8)
26,27
0.8 (0.4–1.6)
-

Continuous analysis§ 0.95 (0.75–1.20), p = 0.67
Continuous analysis§ 0.95 (0.82–1.10), p = 0.50
Social class||
I or II
12,14
0.8 (0.3–1.9)
-
25,17
1.6 (0.8–3.4)
1.4 (0.7–3.1)

III
21,22
0.8 (0.3–2.1)
-
38,41
1.0 (0.6–1.9)
1.0 (0.6–1.9)

IV
15,15
0.9 (0.4–2.2)
-
46,47
1.1 (0.6–1.9)
1.1 (0.6–2.0)

V or VI
22,19
1.0
-
44,48
1.0
1.0

Continuous analysis§ 1.06 (0.86–1.32), p = 0.58
Continuous analysis§ 0.92 (0.78–1.09), p = 0.35
Marital status
Married
67,74
0.4 (0.1–1.2)
0.5 (0.2–1.7)
152,150
1.4 (0.4–4.4)
1.2 (0.4–4.0)

Unmarried
12,5
1.0
1.0
5,7
1.0
1.0
Father's age (years)
<25
18,19
0.7 (0.3–1.6)
0.6 (0.2–1.4)
30,25
1.1 (0.6–2.2)
1.2 (0.6–2.5)

25–29
27,19
1.0
1.0
53,50
1.0
1.0

30–34
11,15
0.5 (0.2–1.3)
0.5 (0.2–1.5)
42,44
0.9 (0.5–1.6)
0.9 (0.5–1.7)

35–39
10,11
0.6 (0.2–1.7)
0.6 (0.2–1.7)
15,16
0.9 (0.4–2.0)
0.7 (0.3–1.7)

40+
5,7
0.5 (0.1–1.8)
0.5 (0.1–1.7)
13,18
0.7 (0.3–1.6)
0.6 (0.2–1.5)

Continuous analysis§ 0.98 (0.93–1.02), p = 0.35
Continuous analysis§ 0.96 (0.93–1.00), p = 0.07
Mother's age (years)
<20
13,7
1.4 (0.5–4.2)
0.9 (0.3–3.2)
6,12
0.5 (0.2–1.5)
0.9 (0.2–3.5)

20–24
24,22
0.9 (0.4–1.9)
0.7 (0.3–1.7)
58,53
1.1 (0.7–1.9)
1.1 (0.6–2.0)

25–29
25,22
1.0
1.0
50,50
1.0
1.0

30–34
12,18
0.5 (0.2–1.4)
0.5 (0.2–1.3)
24,29
0.8 (0.5–1.6)
0.7 (0.3–1.4)

35+
5,10
0.4 (0.1–1.4)
0.4 (0.1–1.3)
19,13
1.4 (0.6–3.4)
1.7 (0.6–4.5)

Continuous analysis§ 0.97 (0.92–1.03), p = 0.37
Continuous analysis§ 0.99 (0.94–1.04), p = 0.69
Urban status
Urban
47,54
0.7 (0.3–1.3)
0.6 (0.3–1.4)
94,96
0.9 (0.6–1.5)
0.9 (0.5–1.5)

Non-urban
31,24
1.0
1.0
63,61
1.0
1.0

* The numbers are for cases and controls who contributed to the unadjusted analyses. In adjusted analyses, they vary depending on missing values in each variable in the model.

The confounders included for each variable are, (a) parity: social class; (b) social class: none; (c) marital status: mother's age; (d) father's age: social class; (e) mother's age: social class and, (f) urban status: social class.

Reference category.

§ The result is the odds ratio that occurs as the variable increases by one unit, either by one year or one social class category (poorer) or one child, adjusted with confounders used in the categorical analyses.

|| Category I represents those of highest socio-economic level, while VI the lowest socio-economic level.

** The confounders included for each variable are, (a) parity: none; (b) social class: mother's age; (c) marital status: mother's age; (d) father's age: social class & parity; (e) mother's age: social class & parity and, (f) urban status: social class & parity.

Wong and Dockerty BMC Blood Disorders 2006 6:5   doi:10.1186/1471-2326-6-5